This invention relates to tetravalent organotin compounds, particularly organotin functionalized silanes, a solid prepared by chemically bonding the organotin functionalized silane to an inorganic support containing surface hydroxy groups; a catalyst prepared from said supported organotin functionalized silane; a continuous or batch process for conducting esterification, or transesterification reactions, and urethane, urea, silicone, or amino forming reactions utilizing said solid supported catalyst and the reaction products of such continuous or batch processes involving the separation of the solid tin-containing catalyst from the liquid reaction products to yield tin catalyzed product containing very low levels of tin.
Homogeneous organotin compounds are known to be effective catalysts for esterification, transesterification, siloxane, and urethane forming reactions by those skilled in the art. However, separation of the homogeneous organotin catalysts from the reaction products is a major disadvantage which is frequently not possible or requires special treatment that usually destroys the catalyst. Homogeneous catalysts are in the same phase, usually liquid, as the reactants and reaction products. Heterogeneous catalysts are of a different phase than the reaction products.
Many types of heterogeneous catalysts are known and have a number of significant advantages over homogeneous catalysts such as ease of separation of the catalyst from the reaction products facilitating re-use of the catalysts and high mechanical and thermal stability over a wide range of processing conditions. Heterogeneous catalysts are sometimes not as selective as homogeneous catalysts. Supported metal complexes, metal complexes attached to the support by a chemical bond, are often as selective as their homogeneous counterparts.
There are two types of supports for heterogeneous catalysts, polymeric and inorganic. Polymer supports are popular because they are easily functionalized and have a flexible structure facilitating interactions between active catalyst sites and reactants. Polymer supports though have several significant disadvantages such as poor mechanical properties, limited thermal stability typically below 160xc2x0 C., and a lack of physical rigidity over a wide range of processing conditions making control over the porosity and diffusional characteristics difficult.
Most known polymeric organotin compounds are not effective catalysts because of they do not possess the desired functionality for esterification; and transesterification reactions, urethane, urea, silicone, and amino forming reactions or the fact that the tin tends to leach out too quickly from the polymer so that only a few reactions may be conducted. Jiang, et al in U.S. Pat. Nos. 5,436,357 and 5,561,205 have disclosed polymeric organotin compounds in which the organotin is attached to the polymer via a non-labile bond and found to be effective for transesterification reactions. However, the polymeric organotin compounds are limited to reactions temperatures in the range of 50 to 150xc2x0 C. and thus are not expected to be effective for esterification reactions, typically carried out at temperatures exceeding 200xc2x0 C. when homogeneous organotin catalysts are used.
Inorganic supports have a number of distinct advantages over polymer supports. They have a rigid structure which allows greater control over the porosity and diffusional characteristics of the support and are not affected by process conditions. The thermal stability is usually limited by the stability of the supported complex and not by the support itself. They also have high mechanical stability that prevents physical breakdown of the particle and the formation of xe2x80x9cfines.xe2x80x9d Metal oxides are the most frequently used inorganic support owing to the fact that metal oxides contain surface hydroxyl groups which can be readily functionalized. Two modes of attachment are generally used for supporting complexes on the surface of metal oxides. The first is through the use of a metal complex that contains a labile ligand capable of reacting with the surface hydroxy groups to give a reaction product in which the metal center in the complex is directly bonded to the surface through an oxygen atom.
{E}xe2x80x94OH+Xxe2x80x94Mxe2x86x92{E}xe2x80x94Oxe2x80x94M+HX
where
{E}xe2x80x94OH=metal oxide
M=metal center in the complex
X=labile ligand
Typically, the preferred mode of attachment of the metal complex is through the use of a functionalized silane that contains labile ligands on the silicon capable of reacting with the surface hydroxy groups of the metal oxide support such as                     {        E        }            ⁢      xe2x80x94OH        +                  X        3            ⁢              SiY        ⟶                  {          E          }                    ⁢              xe2x80x94Oxe2x80x94        ⁢        SiY            ⁢              xe2x80x83            ⁢      where                          {        E        }            ⁢      xe2x80x94OH        =          metal      ⁢              xe2x80x83            ⁢      oxide                  X      =      MeO        ,    EtO    ,    Cl    ,    …        Y    =          functional      ⁢              xe2x80x83            ⁢      group      
Leaching of the metal complex from the surface can be serious if there is any degree of dissociation of the metal under reaction conditions.
Most known organotin compounds are not suitable for preparing the heterogeneous catalysts of this invention because they either do not have the desired functionality for esterification, transesterification, and urethane, urea, silicone, and amino forming reactions, cannot be modified to contain such functionality, or do not form stable bonds with inorganic supports. The synthesis of several silylmethyltin trichlorides and bis(silylmethyl)tin dichlorides have been reported by Mironov, V. F., Stepina, E. M., and Shiryaev, E. M., Zh. Obshch Khim., 42 631 (1972); Mironov, V. F., Shiryaev, E. M., Yankov, V. V., Gladchenko, A. F. and Naunov, A. D., Zh. Obshch Khim., 44, 806 (1974); Mironov, V. F., Shiryaev, V. I., Stepina, E. M., Yankov, V. V., and Kochergin, V. P., Zh. Obshch Khim., 45, 2448 (1975), but do not disclose or suggest bonding these compounds to an inorganic support nor have they determined their effectiveness as catalysts. Similarly, Auner, N. and Grobe J., Z. Anorg. Allg. Chem. 500, 132 (1983) reported a number of 3-silylpropyltin trichlorides but do not disclose or suggest bonding these compounds to an inorganic support and have not determined their effectiveness as catalysts. Schumann, H and Pachaly, B., Angew. Chem. Int. Ed. Engl., 20, 1043 (1981); Schumann, H., and Pachaly, B., J. Organometal. Chem., 233, 281 (1982); Schumann, H., and Pachaly, B., Ger. Offen. 3116643, disclosed several organotin compounds that were supported on alumina and silica, however, they either do not contain the desired functionality for catalysis or there is a labile bond between the silicon and the tin. Matlin, S. A. and Gandham, P. S., J. Chem. Soc., Chem. Commun., 798 (1984) reported the use of an organotin dimethoxide linked to the surface of silica that is effective as a hydride transfer catalyst for the reduction of ketones and aldehydes.
It is the object of this invention therefore, to produce organotin functionalized silanes wherein the organotin is linked to the silane by a stable ligand group(non-labile at both the tin and silicon ends), at least one of the ligands on the silane end of the molecule is labile and results in a stable is silicon oxygen bond with the surface of the inorganic supports, and at least one of the ligands on the tin end of the molecule is a labile group.
Another object of this invention is to prepare a solid comprising an organotin functionalized silane on an inorganic support, which is useful in preparing a transesterification, esterification, or urethane forming catalyst.
A further object of this invention is to prepare a heterogeneous catalyst for transesterification, esterification, or urethane, urea, silicone, and amino forming reactions which has high selectivity, high activity and long catalyst life.
Yet another object of this invention is to provide a process for conducting transesterification, esterification, and urethane, urea, silicone, and amino forming reactions.
This invention provides four compositions of matter comprising: (1) an organotin silane; (2) a catalytically active functionalized organotin silane; (3) an organotin silane on a solid support comprising a metal oxide with surface hydroxy groups and, (4) catalytically active functionalized organotin silane on a solid support comprising a metal oxide with surface hydroxy groups. The formula for each is given in the detailed description.
Also provided is a solid supported organotin resulting from the reaction product of organotin silanes with solid metal oxides containing surface hydroxyl groups, such as glass, silica, mica, silica gel, alumina, aluminasiloxanes, kaolin, titania, zirconia and chromium oxide which have been discovered to be excellent heterogeneous catalysts for esterification or transesterification reactions or urethane, urea, silicone, and amino forming reactions.
A class of supported functionalized organotin silanes have been discovered to be excellent heterogeneous catalysts for esterification or transesterification reactions or urethane, urea, silicone, and amino forming reactions.
This invention also provides an improved process for conducting esterification or transesterification reactions or urethane, urea, silicone, or amino forming reactions comprising the steps of reacting non-solid phase reactants for an esterification or transesterification reaction or urethane, urea, silicone, or amino forming reaction in the presence of a catalytically effective amount of a solid supported organotin silane and separating from said solid catalyst, a non-solid phase containing the products of the reaction.
This invention further comprises the reuse of the heterogeneous catalyst after separating said solid catalyst from the reaction products.
Also provided is a continuous esterification or transesterification reaction or urethane, urea, silicone, or amino forming reactions comprising continuously reacting the reactants for an esterification or transesterification reaction or urethane, urea, silicone, or amino forming reaction in a reactor containing a catalytically effective amount of a solid supported organotin silane catalyst and continuously separating a non-solid phase containing the products of the reaction from said solid catalyst. Also provided is the reaction product of an esterification or transesterification reaction or urethane, urea, silicone, or amino forming reaction catalyzed with said solid supported organotin silanes catalyst and containing less than 100 ppm tin after separating the non-solid phase containing the products of the reaction from said solid heterogeneous catalyst.
Improved synthesis of organotin silanes is also provided involving the reaction of 1,1-dihalosilacycloalkane (e.g. 1,1-diclorosilacyclobutane) with tin tetrachloride to give the corresponding 3-silapropyltin trichloride compounds in the presence of a catalytically effective amount of a Lewis acid such as aluminum trichloride to yield a mixture of 3-(trihalorosilyl)propyl tin trihalide, such as 3-(trichlorosilyl)propyl tin trichloride and di-(3-trihalosilyl)propyl tin dihalide such as di-3-(trichlorosilyl)propyl tin dichloride. Novel syntheses involving ring opening is provided for producing organotin fluctional silanes in which a Lewis acid catalyst is used in the reaction of a dihalosilacycloalkane such as 1,1-dichlorosilacyclobutane with an organotin halide, such as butyltin trichloride to open up the silacyclobutane ring and yield 3-(trihalosilyl)propyl organotin halides such as 3-(trichlorosilyl)propyl butyltin dichloride. If the chloride functionality in the dichlorosilyacyclobutane is replaced with dialkoxy or diaryloxy functional groups, then the need for a Lewis acid catalyst is eliminated in the ring opening reaction to produce organotin silanes.
This invention provides four compositions of matter comprising: (1) an organotin silane; (2) a catalytically active functionalized organotin silane; (3) an organotin silane on a solid support comprising a metal oxide with surface hydroxy groups and, (4) a catalytically active functionalized organotin silane on a solid support comprising a metal oxide with surface hydroxy groups.
The formula (hereinafter referred to as Formula 1) for the organotin silane is 
wherein:
each R1 is independently selected from the group consisting of F, Cl, Br, I, OR, and R, where R is substituted or unsubstituted C1 to C12 alkyl, C5 to C12cycloalkyl, or aryl, provided at least one value of R1 is selected from among F, Cl, Br, I, and OR
each R2 is independently selected from R1, benzyl, vinyl, allyl, hydride, and 
provided at least one value of R2 is F, Cl, Br, I, or OR
R3 is (CH2)m, aryl or cycloalkyl,
m=0 to 17, n=1 to 18, sum of n plus m=1 to 18 except when R3 is aryl or cycloalkyl then n=at least 2,
except, when R3=(CH2)m, m=0, at least one value of R1is Cl, methoxy or ethoxy, or
when R2 is 
then, all of the values of R2 cannot be selected from Cl and I; and,
except also, when R3=(CH2)m, the sum of n plus m=2, 4, 5 or 6, all values of R1 are R with R being aryl or C1 to C12 alkyl, one value of R2 is Cl, aryl or hydride;
then, all remaining values for R2 cannot be selected from C1 to C12 alkyl, C7 to C8 cycloalkyl or aryl; and,
except also, when R3=(CH2)m, the sum of n plus m=3, at least one value of R1 is Cl, all other values of R1 are selected from Cl, CH3, vinyl, or phenyl and one value of R2 is Cl;
then, all remaining values of R2 cannot be selected from among Cl and methyl; and
except also, when R3=(CH2)m, the sum of n plus m=4, all values of R1 are Cl, and two values for R2 are Cl then the remaining value for R2 cannot be butyl.
The formula (hereinafter referred to as Formula 2) for the catalytically active functionalized organotin silane: comprising a compound of the formula: 
wherein:
each R1 is independently selected from the group consisting of F, Cl, Br, I, OR, and R, where R is substituted or unsubstituted C1 to C18alkyl, C5 to C12 cycloalkyl, or aryl, provided at least one value of R1 is selected from among F, Cl, Br, I, and OR;
each R2 is independently selected from R1, benzyl, vinyl, allyl, hydride, hydroxide, sulfide, sulfate, carbonate, phosphate, phosphite, phosphonate, sulfonate, mercapto, a residue of a mercapto acid, mercapto alcohol, or mercaptoesters, carboxylates substituted or unsubstituted of C1 to about C20, and 
provided at least one value of R2 is selected from among hydroxide, sulfide, sulfate, carbonate, phosphate, phosphite, phosphonate, sulfonate, mercapto, a residue of a mercapto acid, mercapto alcohol, or mercaptoesters, and carboxylates substituted or unsubstituted of C1 to about C20;
R3 is (CH2)m, aryl or cycloalkyl,
m=0 to 17, n=1 to 18, sum of n plus m=1 to 18 except when R3 is aryl or cycloalkyl then n=at least 2,
The formula (hereinafter referred to as Formula 3) for the organotin silane on solid support comprising a metal oxide with surface hydroxy groups is: 
wherein:
each R1 is independently selected from the group consisting of F, Cl, Br, I, Mxe2x80x94Oxe2x80x94, OR, R, where R is substituted or unsubstituted C1 to C18alkyl, C5 to C12 cycloalkyl, or aryl, provided at least one value of R1 is Mxe2x80x94Oxe2x80x94;
each R2 is independently selected from R1, benzyl, vinyl, allyl, hydride, and; 
R3 is (CH2)m, aryl or cycloalkyl
m=0 to 17, n=1 to 18, sum of n plus m=1 to 18 except when R1 is aryl or cycloalkyl then n=at least 2, and Mxe2x80x94Oxe2x80x94 is the metal oxide component of the solid support;
except, when R3=(CH2)m, the sum of n plus m=2, 4, 5 or 6, all values of R1 are R with R being aryl or C1 to C12 alkyl, one value of R2 is Cl aryl or hydride;
then, all remaining values for R2 cannot be selected from C1 to C12 alkyl, C7 to C18 cycloalkyl or aryl; and
except also, when R3=(CH2)m, the sum of n plus m=4, all values of R1 are Cl, and two values for R2 are Cl or when all values of R1 are methoxy and two values for R2 are methoxy, then the remaining value for R2 cannot be butyl.
The formula (hereinafter referred to as Formula 4) for the catalytically active, functionally organotin silane on a solid support comprising a metal oxide with surface hydroxy groups is: 
wherein:
each R1 is independently selected from the group consisting of F, Cl, Br, I, Mxe2x80x94Oxe2x80x94, OR, R, where R is substituted or unsubstituted C1 to C18alkyl, C5 to C12 cycloalkyl, or aryl, provided at least one value of R1 is Mxe2x80x94Oxe2x80x94;
each R2 is independently selected from R1, benzyl, vinyl, allyl, hydride, hydroxide, sulfide, sulfate, carbonate, phosphate, phosphite, phosphonate, sulfonate, mercapto, a residue of a mercapto acid, mercapto alcohol, or mercaptoesters, carboxylates substituted or unsubstituted of C1 to about C20, and 
provided at least one R2 is selected from among hydroxide, sulfide, sulfate, carbonate, phosphate, phosphite, phosphonate, sulfonate, mercapto, a residue of a mercapto acid, mercapto alcohol, or mercaptoesters, and carboxylates substituted or unsubstituted of C1 to about C20;
R3 is (CH2)m, aryl or cycloalkyl;
m=0 to 17, n=1 to 18, sum of n plus m=1 to 18 except when R3 is aryl or cycloalkyl then n=at least 2;
and Mxe2x80x94Oxe2x80x94 is the metal oxide component of the solid support.
The synthesis of the organotin silanes and chemically bonding them to a solid support comprising a metal oxide with surface hydroxy groups is disclosed hereinafter and shown in the examples at least for the preferred embodiments.
A heterogeneous organotin silane catalyst is provided comprising, the organotinsilane of Formulas 3 and 4 are made by chemically bonding (supporting) an organotin silane of Formula 1 or onto a solid metal oxide containing surface hydroxy groups via at least one metal-Oxe2x80x94Si bond. Preferably is the functionalized heterogeneous organotin silane of Formula 4. The compounds of Formula 4 can be synthesized by either by bonding the compound of Formula 2 onto the solid support or by bonding the compound of Formula 1 onto the support and then improving the catalytic functionality by replacing at least one of the labile groups on the tin of Formula 1 with the substituent groups for R2 contained in the Formula 2 verses Formula 1.
Improving the catalytic functionality of Formula 1 or Formula 3 can be increased by converting them to the compounds of Formula 2 and Formula 4 respectively. This is accomplished when the labile group on the tin is replaced by reacting it with a reagent selected from the group consisting of alkali and alkaline hydroxides, oxides, carbonates, bicarbonates, phosphates, phosphinates, sulfates, organic acid salts, sulfonates, alcohols, phenols, and inorganic or organic acids. This results in a class of supported functionalized organotin silanes that have been discovered to be excellent heterogeneous catalysts for esterification or transesterification reactions or urethane, urea, silicone, and amino forming reactions. For catalytic properties, the key requirement for this functional group is that it result in a labile bond with the tin under reactions conditions typically used for esterification or transesterification reactions or urethane, urea, silicone, and amino forming reactions. The catalytically active groups on the tin include F, Cl, Br, I, Mxe2x80x94Oxe2x80x94, OR, benzyl, vinyl, allyl, hydride, hydroxide, sulfide, sulfate, carbonate, phosphate, phosphite, phosphonate, sulfonate, mercapto, a residue of a mercapto acid, mercapto alcohol, or mercaptoesters, carboxylates substituted or unsubstituted of C1 to about C20. However the preferred groups are Cl, Or, oxide, hydroxide, sulfonate, or carboxylates substituted or unsubstituted of C1 to about C20.
The supported organotin silanes compounds of Formula 3 and Formula 4 have been discovered to be excellent heterogeneous catalysts for esterification or transesterification reactions or urethane, urea, silicone, and amino forming reactions.
Organotin silanes of the Formula 1 in which m equals 0 and n plus m equals 3 can be produced utilizing a novel ring opening reaction of silyacyclobutanes with tin halides followed by subsequent functionalizing with the above stated reactions. The only reported examples of such a ring opening reaction were limited to the reactions of 1,1-dichloro and 1,1-dimethylsilacylobutane with tin tetrachloride to give the corresponding 3-silylpropyltin trichloride compounds. Although the reaction of 1,1-dichlorosilacyclobutane with tin tetrachloride is reported by Auner and Grobe, it was found that this reaction does not occur in significant conversion of the silacyclobutane to give the expected organotin silane. Surprisingly it was found that by adding a small amount of a suitable Lewis acid catalyst, such as aluminum trichloride, the reaction occurred to give a mixture of 3-(trichlorosilyl)propyl tin trichloride and di-3-(trichlorosilyl)propyl tin dichloride. Using a Lewis acid catalyst, 1,1-dichlorosilacyclobutane reacts with organotin halides, such as butyltin trichloride to open up the silacyclobutane ring and give 3-(trichlorosilyl)propyl butyltin dichloride.
It has been discovered that the reaction of tin tetrahalides and organotin halides with 1,1-dialkoxysilacyclobutanes proceed without the need for a catalyst.
An improved esterification or transesterification reaction or urethane, urea, silicone, or amino forming reaction is provided of the type comprising reacting non-solid phase reactants for an esterification or transesterification reaction or urethane, urea, silicone, or amino forming reaction wherein the improvement comprises the steps of reacting said non-solid phase reactants in the presence of a catalytically effective amount of a solid supported organotin silane catalyst of the present invention (Formula 3 or Formula 4), and separating from said solid catalyst a non-solid phase containing the products of the reaction. This results in a reaction product that has been catalyzed with a tin containing catalyst and contains very little tin after the phase separation operation in which the solid catalyst is separated from the non-solid reaction product. Phase separation operations such as liquid-solid and gaseous-solid separation operations are well known unit operations in chemical engineering and practiced commercially. Filteration, centrifugation, settling, and entrainment are but a few known unit operations that use phase differences to effect a separation of materials. In addition, separation can be effectuated when the solid catalyst is in a reactor such as a packed bed or column into which non-solid reactants are added and non-solid reaction products are removed, thereby effectuating the separation of non-solid reaction products from the solid catalyst. A reactor containing solid catalyst of the present invention can be used to continuously conduct esterification or transesterification reaction or a urethane, urea, silicone, or amino forming reaction. This is accomplished by continuously adding non-solid reactants to a reactor containing the catalyst and continuously removing from the reactor a stream containing non-solid reaction products.
Whether practiced continuously or batchwise, after separation of the solid catalyst from reaction products, the reaction products are surprisingly low in tin impurities, generally less than 100 ppm and can be less than 10 ppm. This purity is accomplished by a simple phase separation in which the solid (heterogeneous) catalyst is separated from the non-solid, usually liquid, reaction products. Also, this purity is due to the fact that the tin catalyst is not readily extractable from it""s solid support due to the strong bond between the support and the organotin silane achieved by the Mxe2x80x94Oxe2x80x94Si bond. Reducing or eliminating tin impurities is an important consideration when the reaction product of an esterification or transesterification reaction or urethane, urea, silicone, or aminos forming reaction will be used in food contact applications, e.g. containers, or for human ingestion such as pharmaceutical products.
The heterogeneous organotin silane catalyst is a solid supported organotin silane resulting from the reaction product of an organotin silane of Formula 1 or Formula 2 with a solid support having a metal oxide containing hydroxyl groups on the surface of the solid support. Examples of suitable metal oxide materials are glass, such as silica, mica, silica gel, alumina, aluminasiloxanes, kaolin, titania, zirconia and chromium oxide. Suitable supports can be solid, hollow or porous particles of such materials or composites having such materials on the surface of the particle. The present invention is independent of the shape and size of the solid support. While beads are a common shape for supports, any convenient shape and size may be utilized and selected for practicing the present invention based on considerations such as a good surface area to weight ratio and/or ease of separation of the solid catalyst from the non-solid reaction products.
One or more of the labile groups (i.e. F, Cl, Br, I, or OR) on the tin of the supported catalyst defined by Formula 1 and Formula 3 is preferable replaced with a group having improved catalytic properties. This can be accomplished by reacting the organotin silane, either before or after in is bonded to the support (after is preferred), with a wide variety of reagents such as alkali and alkaline hydroxides, oxides, carbonates, bicarbonates, sulfates, phosphate, phosphite, phosphinate, organic acid salts, sulfonates, and by reaction with alcohols, phenols, acids (both inorganic and organic), and other reagents known to those skilled in the art for substituting the halide functionality on an organotin halide. This results in the labile group (i.e. F, Cl, Br, I, or OR) on the tin being replaced with a functional group such as oxide, hydroxide, carboxylate, bicarboxylate, sulfate, organic salt, sulfonate, phenol, inorganic or organic acids, mercaptide, phosphate, phosphite, phosphinate and carbonate. Although the organotin silane with the halide labile group on the tin is catalytically active, preferably, the halide group on the organotin silane is replaced with another functional group by the reaction discussed above. Adding the improved catalytical functionality to the organotin silane after it has been reacted with the metal oxide containing support is preferred because it avoids the labile group or groups on the silane from being also replaced with the functional group. The labile group of groups on the silane are better utilized as the site for forming the Mexe2x80x94Oxe2x80x94Si bond for chemically attaching the organotin silane to the support.
A novel, ring opening, synthesis has been discovered for a subgroup of the organotin silanes of Formula 1. The subgroup has the formula: 
wherein R1 and R2 have the same values as in Formula 1.
The synthesis can be best described by the following general reaction scheme using Cl for R1 and R2 and AlCl3 for the Lewis Acid catalyst. It should be understood that R1, and R2 can have any of the values given in Formula 1 and any Lewis Acid catalyst can be used. 
Where n=1 to 4
In this general reaction scheme the Lewis acid (aluminum trichloride) will catalyze the reaction of any organotin halide with 1,1-dihalosilacyclobutane and in which R can be alkyl or aryl (unsubstituted or substituted), alkylene or the silyl group itself X3Si(CH2)3xe2x80x94.
The reactions will give a product or a mixture of products depending on the value of n in the general reaction scheme. These are shown for the series of reaction for each value of n: 
Furthermore, AlCl3 is well known to those skilled in the art as an effective catalyst for the redistribution reaction of organotins. There are potentially other species that may be formed by the scrambling or R, Cl3Si(CH2)3xe2x80x94, and Cl groups on the tin which exist in equilibrium. Accordingly, the product is better described as a reaction product rather than by the above structural formula. The relative amounts of the reaction products in the mixture will vary depending on the mole ratio of the reactants, that is the mole ratio of the 1,1-dichlorosilacyclobutane reacted with the halide.
Also discovered is another synthesis not requiring a Lewis acid catalyst involving the reaction of 1,1-dialkoxysilacyclobutane, such as 1,1-dimethoxysilacyclobutane, with R4xe2x88x92nSnCln. The reactions for different values of R4xe2x88x92n showing the mixtures of reaction products the above, except that the chlorides on the silicon are replaced with ROxe2x80x94 groups, and there is no need for Lewis acid catalyst.
The reactivity of the tin halide decreases with an increase in the organic functionality on the tin, i.e. the reactivity decreases in the order SnCl4 greater than RSnCl3 greater than R2SnCl2, and R3SnCl. This is particularly true for the uncatalyzed reactions.
Synthesis of Type A Organotin Functionalized Silanes
1,1-Dichlorosilacyclobutane (7.14 grams) and tin tetrachloride (13.70 grams) were transferred into a tube under nitrogen. The tube was sealed and placed in oil bath and held at 132xc2x0 C. for 18.5 hours. Analysis of the reaction mixture by 119Sn and 29Si NMR indicated virtually no reaction had occurred.